Wave impulse generator



Oct. 29,1946.

TIME Mam/u ran I I C. V. LITTON WAVE IMPULSE GENERATOR Filed Feb. 25, 1942 S/G/VAL Sal/176E IMPULSE SOURCE TIME MM/M7278 -1:- I F 6/6/VAL IMPULSE SOURCE SOURCE 2o FlG.3.

INVENTOR.

SIG/VAL SOURCE IMPULSE sou/ms CHARLES K L/TTO/V ATTOR Y. 7 iv Patented Oct. 29,1946

WAVE IMPULSE GENERATOR I I Charles V. Litton, Redwood City, Calif., assignor to International Standard Electric Corporation, New York,N. Y.,.a corporation of Delaware Application February 25, 1942, Serial No. 432,226

' Claims. I 1

This invention relates to impulse generators and more particularly to high power waveimpulse generators and transmitters.

At the present time considerable attention is being given to so-called pulse transmission systems. These systems are proposed for transmission of wave-impulse (i. e. very brief trains of ultra-high frequency carrier waves) for object detection such as in the case of airplane detectors. They are also coming into more general use for ordinary communication, for example, with time modulation of the wave-impulses, since tubes may thenbe used at a much higher power level than. incontinuous signaling, as they are needed for only a small percentage of the time.

For this purpose various types of development have been undertaken in an endeavor to produce powerful wave-impulses tuned to a desired ultra-high frequency. Such endeavors have generally been directed to the use of D. C. impulses (i. e. very brief surges of direct current or voltage) for modulating or keying an ultra short wave oscillation generator of conventional. type. Alternatively, it has been proposed to produce wave-impulses at low power levels with cathode ray tubes, and then amplify these low level impulses. One of the diflicultiesof these impulse transmission systems resides in the fact that it is quite difiicult to amplify wave-impulse energy because of the wide wave band involved. It is,

therefore, desirable. if possible, to produce waveimpulses directly at an energy level highenough for transmission.

According. to my invention the powerful waveimpulses for transmission are produced by" use of an abrupt current breaking device operated within a closed vessel, either evacuated or under pressure of some inert I gas, associated with a tuned high quality oscillating circuit, that is, a circuit having a low ratio of resistance to inductive reactance, so as. to induce damped wave trains by shock excitationof said circuit.

The well known spark transmitter is, of course, an impulse generator which produces damped wave trains by shock excitation. However, known spark transmitters are generally arranged to make use of the abrupt circuit. closure caused by gaseous breakdown for effecting the shock excitation. An abrupt circuit interruption is much more suitablev since it may theoretically approach an instantaneous, infinite change of voltage and an infinite rate of change of current instead of merely a finite charge. of voltage and a finite rate of; change of current. Also a spark gap when broken down ofiers efiective resistance which damps the associated circuit to such a degree that it proves impossible to obtain waves to produce extremely short impulses in the trains lasting for hundreds of cycles. Quick quenching gaps do not solve this difficulty for ultra short waves because even the quickest gap has a deionization time of the order of hundreds of cycles of these ultra short waves. Furthermore, the resonant circuits of known spark transmitters generally have too high a ratio of resistance to inductance to produce by. shock excitation a wave train which endures for several hundred cycles before falling to half its initial amplitude. Accordingly, if attempts were made to transmit such ultra short wave impulses over the known type systems energy sent would be so weak that it would be useful for only very short distances.

According to one feature ofv my invention, the abrupt current interruption is produced by a vibratingmember and the tuned circuit is preferably a closed resonant chamber.

In a preferred embodiment of the invention the vibrating member is arranged at least partially within a closed chamber forming the tuned circuit and is vibrated by control impulses which may be time modulated.

A. better understanding of my invention will be had from the particular desscription thereof made with reference to the accompanying drawing in which: U

Fig. 1- is a circuit diagram used to explain my invention;

Fig. 2 is one formof a preferred embodiment of any invention; and

Fig. 3 i another form thereof.

In accordance with the present invention, I propose to utilize a. system in which an abrupt current interruption is produced by means of an enclosed switch arrangement connected-in a circuit, as. shown in Fig. 1. This enclosed switch may then operate in a vacuum or under pressure of. some inert gas so that large currents may be broken substantially instantaneously without arcing at the contacts. closed switch Ml is illustrated as having a contact element It supported' on vibrating rod l2. Rod I2 is vibrated by means of anielectromagnet it by energy applied to the windings of this magnet.-. If the pulses of energy applied to H3 are time modulated, rod i2 is preferably substantially damped. or resonant at a frequency considerably different from the frequency of the energy applied to magnet I3' so that it will be capable of following the time. modulation. Contact H is arranged: in serieswitha source of D. C. voltage In this figure the in- M, which is preferably a source capable of giving a high current for a short period of time. This may, for example, be an ordinary lead cell storage battery. Coupled in this series circuit is a tank circuit diagrammatically shown at l5, consisting of an inductance and a condenser. In actual practice, such a tank circuit should generally consist of a closed resonant chamber in order that an extremely low ratio of resistance to inductance will be achieved. The series circuit is then completed, as magnet I3 is energized, by means of two contact elements I6, I? which are alternately engaged by contact H to cause a high current to flow through the inductance of the tank circuit and then abruptly interrupt such current so as to shock excite circuit l5 which will then oscillate at its resonant frequency. Contacts II, It; and I1 are maintained within the envelope of ID which is either filled with an inert gas under pressure or preferably evacuated to a high degree so that the large currents produced in the circuit may be interrupted substantially without arcing. Thus, upon periodic energization of magnet l3, exceedingly steep wave fronts are produced by each abrupt interruption of the series circuit thus inducing very high power wave trains in tank circuit which may be then radiated from antenna H3 or transmitted to any other load circuit. Preferably the capacity between l2 and l6, I! should be as small as possible. Also the coupling to antenna I8 should be loose enough so that the Waves in 15 are not too highly damped.

In the preferred arrangement, the impulse transmitter according to my invention is used with a time modulation system. This is shown diagrammatically in Fig. 1 in which the impulse source produces spaced D. C. impulses which are time modulated by signals from source 2! in the time modulation circuit 22. Details of this system are not disclosed in the present application since they form no part of the present invention. Systems of this type, however, are known and these systems operate by causing a time displacement of the impulses in accordance with applied signals so that these signals may be reproduced at the receiving end. This type of system is shown, for example, in U. S. patent to A. H. Reeves, No. 2,266,401, dated December 16, 1941.

The time modulated D. C. impulses are then applied to the winding of relay l3 to operate switch It! so that wave impulses corresponding to these time modulated D. C. impulses but of great power are applied to load I 8.

The showing of Fig. 1 illustrates the tuned circuit conventionally as a coil and a condenser. In actual operation, however, such a circuit is difiicult to make of high enough quality for the purpose of my invention. For this reason, it is preferred to use some form of closed resonant chamber. Fig. 2 illustrates one form of my invention using such closed resonant circuit. In this figure the impulse source 20, signal source 2|, time modulator 22 and control magnet I3 are shown in the same relationship as shown in Fig. 1. However, in place of the tuned circuit I5, I provide a closed resonant chamber 25 to which the load antenna I8 is coupled by means of a coaxial line 25 and a loop 21. The inclosed switch is preferably attached directly to a portion of the walls of resonant chamber 25 so that this chamber 25 forms in part an envelope for the inclosed switch. The magnetically controlled vibrating member 32 of the switch 30 extends outwardly from chamber 25, the upper end of this member 32 being substantially in line with one of the walls of the chamber. Contacts 36, 31 are directly connected to chamber 25 and may be made integral therewith if desired. Thus, as member 32 is vibrated by D. C. control impulses in the windings of relay l3, source 24 is permitted to complete a direct current circuit. Upon breaking this circuit, the impulses of direct current produce shock excitation of the resonant circuit 25. In order that the direct current supply may be well distributed, it is preferable that separate parallel connection from battery M to different parts of chamber 25 be made. Accordingly, I provide a number of separate leads 24 from battery M to different points on the Walls of resonant chamber 25.

A still further modification of a circuit in accordance with my invention is shown in Fig. 3. This system is substantially similar to that shown in Fig. 2 except that tuned resonant chamber 25 is not made annular in form as in Fig, 2. Furthermore, instead of sealing the glass envelope to a metal member forming part of the chamber, a portion of the glass envelope inclosing switch 39 is merely extended into the chamber through an opening in disc 38 which forms one inclosing end Wall of resonant chamber 25. This particular construction in many cases may be preferable to that in Fig. 2.

While I have described above the principal features of my invention and several specific embodiments thereof, it should be distinctly understood that this description is made by way of illustration and not as a limitation on the scope of my invention. The features of my invention may be readily applied to many different structural arrangements which will present themselves to one skilled in the art to which this invention appertains.

What is claimed is:

1. An impulse generator for generatingzshort wave trains of high power comprising a source of direct current energy, an enclosed vibrator switch arrangement in series circuit with said source, electro-mechanical means for operating said switch arrangement to alternately make and break said series circuit to produce high current impulses, and a tuned circuit comprising asubstantially closed resonant chamber forming at least part of the envelope of said enclosed switch and arranged in circuit with said switch for shock excitation by said impulses.

2. An impulse generator according to claim 1 further comprising a time modulated impulse means for controlling said electro-mechanical means, and an output circuit'coupled to said tuned circuit.

3. An impulse transmitter system. comprising a source of direct current energy, an inclosed switch in series with said source for making and breaking a direct current circuit including said source, electro-magnetic means for operating said inclosed switch, impulse means to operate said switch to produce high power direct current impulses, a resonating circuit tuned to a selected radio frequency comprising a substantially closed resonant chamber forming at least a part of the envelope of said enclosed switch arranged for shock excitation by said impulses and coupled to said direct current circuit, and an output circuit coupled to said tuned circuit.

1. An impulse transmitter according to claim 3, further comprising means for time modulating impulses from said impulse means, whereby energy in said output circuit consists of high power time modulated radio frequency impulses.

5. An impulse generator for generating short wave trains of high power comprising a source of direct current energy, a stationary contact and a vibratory contact in series with said source, electromagnetic means for operating said vibratory contact to alternatively make and break said series circuit to produce impulses, a tuned circuit comprising a substantially closed annular resonant chamber forming at least a part of a gastight enclosure for said contacts and arranged in circuit with said contacts for shock excitation by said impulses, and an output circuit coupled to said resonant chamber.

CHARLES V. LITTON. 

